(1) Field of the Invention:
This invention relates to sail devices and more particularly to a sail device adapted to small ships.
(2) Description of the Prior Art:
Various ships utilizing sails are recently suggested from the viewpoint of saving energy.
Now, sails are largely divided into soft sails and hard sails and either must be folded when the wind is too strong. As a method of folding the sail, for soft sails, there is taken a method wherein a sail is wound inside or outside a mast. On the other hand, for hard sail, there is a method wherein a hard sail is divided into many small sails which are slid along a frame (the gazettes of Japanese patents laid open Nos. 25644/1980 and 116593/1981) or a method wherein a hard sail is divided in the same manner into small sails which are rotated like window blinds (the gazette of Japanese patent laid open No. 47296/1982). However, either is considerably complicated in the structure.
Also, in order to improve the air force characteristic of sails, for examle, for soft sails, hard sails are combined with a soft sail at both ends and a yard is curved forward (the gazettes of Japanese patents laid open Nos. 58594/1982 and 63595/1981) and, on the other hand, for hard sails, a hard sail itself is formed as curved to be of a predetermined curved surface. However, either is considerably costly for such information.
On the other hand, the convenience of using a sail and engine in common is recognized in such small ships as fishing boats. However, the sail of the above mentioned already suggested method or system can not be directly applied in view of the structure and cost. Therefore, the present inventors have repeated hard reserches to develop a sail well applicable even to small ships and, as a result, have obtained a conclusion that, though there has been formed a fixed conception that a sail itself must be formed as curved to be of a predetermined curved surface because the air force characteristic is considered too much in the conventional sail, in order to perform the role as of a sail, the sail need not always be of a curved surface but may be of a shape which can utilize the wind force in short.